The present invention is generally related to optic fiber networks, and in particular, provides an attenuator for controllably varying the strength of an optical signal.
In fiber optic networks, light signals are transmitted along optical fibers to transfer information from one location to another. It is often desirable to tailor the power of optical signals within optical fiber networks. For example, the individual components of an optical fiber network may be tested using a low power optical signal to simulate fiber optic telecommunications or data communications over a long distance. Tailoring of optical signal strengths is desirable within automatic optical testing systems, optical signal routing systems, optical sensor arrays, and the like.
Although the propagation of light signals within optical fibers is somewhat analogous to the transmission of electronic data along metal wires, manipulating the strength of an optical signal within an optical fiber is more problematic than varying the strength of an electrical signal along a wire. Electrical signal strength can be varied simply by generating a different input voltage, or by coupling the wire to a ground through a variable resistor. Optical signals are typically generated by laser diodes, and, unfortunately, laser diodes can be less flexible than electrical signal generators.
Furthermore, once the signal has entered the optical fiber, selectably and repeatably removing or blocking a portion of the optical signal is more challenging than simply varying a resistor. Although optical signals can be filtered while they are transmitted between aligned ends of optical fibers, such arrangements are susceptible to both misalignment and contamination. Single mode optical fibers are particularly susceptible to such misalignment and contamination, as their core diameters are typically as small as 2 to 10 .mu.m. Hence, even minute particles can block a substantial portion of the signal.
In light of the above, it would be desirable to provide improved structures and methods for attenuating optical signals. It would be particularly desirable if such improved structures avoided precise alignment requirements, and were controllably and repeatably variable throughout a wide range of attenuation values.